Accession Number:

ADA250335

Title:

Strain Rate and Stress Relaxation Effects on Pressuremeter Testing in Clays

Descriptive Note:

Final rept. 1 Aug 1989-31 Dec 1991,

Corporate Author:

PURDUE UNIV LAFAYETTE IN SCHOOL OF CIVIL ENGINEERING

Report Date:

1992-03-01

Pagination or Media Count:

283.0

Abstract:

This research was undertaken to answer issues related to cavity expansion and in-situ testing using the pressuremeter. Emphasis of the research was placed upon validating the fundamental concepts underlying the cylindrical cavity expansion theory. Test were performed in a cuboidal shear device CSD at strain rates of 0.01, 0.05, 0.10, 0.50, 1.00 and 5.00 per minute on artificially sedimented specimens of kaolin clay and a kaolin-ground silica mixture with a plasticity index in the range similar to most clays. It was found from the experiments that the normalized shear strength with respect to 0.01min increases linearly with the logarithm of strain rate. The increase in undrained shear strength in the pressuremeter stress path is about 14.3 per log cycle for kaolin clay and 15-3 for the kaolin-silica mixture. The undrained shear strength in the conventional triaxial test was found to increase about 8 to 10 for a tenfold increase in strain rate. Therefore, it can be concluded that the undrained shear strength increases about 40-50 more in pressuremeter stress path tests than in the triaxial stress path tests. A new state variable, indicative of the fabric of clays is introduced. Based on these concepts and a general failure criterion, a simple model to predict failure parameters of anisotropic clays for many commonly encountered stress paths was developed. The model capability to interpret in situ strength measured under a given stress path and transfer it to another stress path was illustrated. Finally, the ability to obtain failure parameters for any stress path using data from a single CIUC test was demonstrated.

Subject Categories:

  • Soil Mechanics
  • Test Facilities, Equipment and Methods

Distribution Statement:

APPROVED FOR PUBLIC RELEASE